how is ti not? i mean they werek inda of the same hiyori was a worm behaving and acting like a normal person andtsurugi was a worm behaving like a normal person yet tendou killed tsurugi just because he was a worm

It was more or less an understanding. Tsurigi had a dream to rid the world of all worms, which couldn't come to fruition if he was still alive. Thats why he lead all the remaining worms into an ambush for the Riders to kill, and ultimately let Tendou kill him.

I'm pretty sure if I found out I was the monster that killed my sister, I'd want Tendou to take me out, too.

They had a conversation about it, right? Kagami was saying pretty much the same thing. He tried to say that Tsurugi could live like a human, like Hiyori and Tadokoro. But Tendou explained the exact thing Take-sempai said about Tsurugi actually hurting/killing innocent people, including Tsurugi and his sister.

So yeah. I always thought it sucked and it was really sad because I liked Tsurugi. They also spent tons of episodes showing what a goof he is, establishing that he really never wanted to hurt anyone. At the same time, the fact he couldn't control it was another contributing factor. So it sucked. But it made perfect sense.